Water flooding method using gel and viscosity-increasing materials

ABSTRACT

A water flooding method wherein gel and viscosity-increasing materials are separately, intermittently injected into a stream of floodwater being injected into one or more wells to develop and maintain a uniform flood front.

P197912 OR 3963215729 wmuwea ounce I aware [1 1 3,63,729 Parker 1 1 Feb.1, 1972 [541 WATER FLOODHNG METHOD USING 2,874,545 2/1959 Twining166/294 x GEL AND VISCQSITYJNCREASHN 3,302,717 2/ 1967 West et a]166/283 G 1 et a1 1 3,402,137 9/1968 Fischer et a1..... ....l66/275 UX[72] Inventor; Barry W, Parker, Lubbock, Tex 3,415,319 12/1968 Gibson..166/295 3,421,582 1/1969 Fallgatter 1 66/273 [73] Assignee: PhillipsPetroleum Company 22 Filed: May 27 1970 Primary Examinerlan A. CalvertAttorney-Young and Quigg [211 Appl. No.1 41,066 w an. 5 a. a.

52 us. (:1 ..l66/273, 166/275 [57] ABSTRACT [51] int. n E2111 43/22 1 Awater flooding method wherein gel and viscosity-increasing [58] Field ofSearch ..166/273-275, 283, materials are separately, intermittentlyinjected into a stream 166/294, 295 of floodwater being injected intoone or more wells to develop and maintain a uniform flood front.

[56] References Cited V M V 9 Claims, No Drawings v a QNI EEIA'LEQBAIEEI2-- 2,827,964 3/1958 Sandiford m1 3,500,929 3/1970 @11 6; et a1,.....

WATER l-LOODING METHOD USING GEL AND VISCOSITY-INCREASING MATERIALS Thisinvention relates to an improved method for water flooding a hydrocarboncontaining formation. ln another aspect, this invention relates to amethod of water flooding a hydrocarbon containing formation by which amore uniform flood front is developed and maintained.

ln heretofore utilized water floods, the floodwater is injecteddownwardly through one or more injection wells, into thehydrocarbon-containing formation and through the formation to drivehydrocarbons contained therein into one or more remotely locatedproducing wells, there to be produced to the surface and captured. Owingto the properties of the floodwater and the formation, injection andsubsequent liquid movement rates through the formation are greater overthe more permeable portions of the formation. Because of this uneveninjection distribution over the thickness of the hydrocarbon-containingformation, sometimes large volumes of hydrocarbons are bypassed by theflooding water.

It is therefore an object of this invention to provide a more efficientwater flooding method for recovering hydrocarbons from a subterraneanformation. Another object is to provide a method for regulating theinjectivity profile of the injection well. Yet another object of thisinvention is to provide a method for developing and maintaining auniform flood front. Other aspects, objects, and advantages of thepresent invention will become apparent from a study of the disclosureand the appended claims.

In the operation of this water flooding method, a subterraneanhydrocarbon-containing fonnation is penetrated by at least one injectionwell and at least one remotely located producing well. It should beunderstood, however, that this invention can be practiced where aplurality of producing'and injection wells are utilized to flood andproduce a common hydrocarbon-containing formation. The relativeplacements of the producing wells are remote from any injection well andcan be in various patterns such as five spots, seven spots, nine spots,etc., as known in the art.

Flood water is injected downwardly through the injection wells into thehydrocarbon-containing formation, thereby forcing hydrocarbons intotheremote producing well where they are produced to the surface andcaptured. A substantially continuous stream of floodwater is injecteddownwardly through one or more injection wells into the formation.Volumes of viscosity increasing material and gel particles areseparately, intermittently injected into the floodwater in the formationeach at spaced apart intervals while hydrocarbons entering the producingwells are produced to the surface and captured.

The following are examples of the viscosity-increasing materials andexamples of the gel particles that can be utilized with this invention.

Viscosity Increasing Material I Gel Particles Partially hydrolyzedpolyacrylamides partially hydrolyzed polyacrylamides carboxymethylcellulose gelled with polyvalent metal ions such as iron or formaldehydeuar gum lignosulfonates gelled with sodium dichromate Kellen 'Kelzan isan xanthan gum product that is classified as a carbohydrate and is acomplex polysaccharide gum having a molecular weight of more than onemillion.

In order to provide a volume of floodwater having sufficient gelparticles to plug a portion of the pore spaces sufficiently large tocause detectable change of flow characteristics through the formation,it is preferred that the gel particles be mixed with the floodwater in aconcentration range of about 0.1 percent to 0.00l percent by volume andthat the total volume of injected mixture be at least 0.5 pore volume.In order to provide another volume of floodwater with sufficientlyincreased viscosity to significantly decrease the fingera'm r ing of thefloodwater through the formation and the development of a more uniformflood front, it is preferred that the viscosity-increasing material bemixed with the floodwater in a concentration range of about 0.05 percentto 0.l percent by volume. Where it is desired to add surfactants, asknown in the art, to the portion of the floodwater containing theviscosity increasing material in order to wet the surfaces of the rockformation, it sometimes becomes necessary to increase the amount ofviscosity-increasing materials added to the floodwater and surfactantmixtures. Where surfactants are present in the floodwater theviscosity-increasing material should be maintained within aconcentration range of about 0.05 percent to 0.20 percent by volume. Atconcentrations greater than listed above, the flood front isunnecessarily restricted from passing through the formation withresultant waste of power, time, and materials. At concentrations lowerthan those listed above, the flood front is not sufficiently uniform,the floodwater fingers through the formation, and sometimes largevolumes of hydrocarbons are bypassed in the formation. It is preferred,however, that the total volume of gel particles injected into theformation be greater than the total volume of viscosity-increasingmaterials injected in order to maintain the process at an economicallyfeasible level while adequately controlling the movement of the floodfront through the hydrocarbon-containing formation. It is also preferredto first inject the viscosity-increasing materials immediately followedby the gel particles. Since the gel suspensions function by poreplugging, that fraction cannot be expected to reach the efficiency ofalldisplacement attained by the viscous fluids by mobility reduction.Preceding the gel particle flooding portion with a volume of viscousflood fraction will thereby produce hydrocarbons beyond those volumesthat can be produced by gel flooding or flooding by floodwater alone.The flood of this invention can also be carried by successfully alteringthe viscosity and gel additives or by periodically following thefloodwater containing the gel particles with a volume of gel wateralone. The duration of each sequence and volume of each liquid mixtureinjected will depend upon the properties of the hydrocarbon-containingformation and the in-place hydrocarbons. These properties can bediscovered as known in the art by core and fluid sample analyses.Injection pressure records and injectivity profile studies during theinjection are also useful tools in determining whether or not theadditives of this invention should be increased or decreased to maintaina uniform flood front.

One example of a flooding method of this invention is as follows:

EXAMPLE On a pore volume (PV) basis the following slugs of material areinjected into an oil reservoir'which preferably has not been previouslywater flooded:

0.1 to 0.2 PV of water viscosified with 500 p.p.m. Kelzan;

0.6 to 0.8 PV of water containing 0.1 volume percent gel particles,these particles being composed of 2,000 p.p.m. partially hydrolyzedpolyacrylamide and 400 p.p.m. ferric chloride hexahydrate; and

0.2 PV water After injecting the above material mixture, water isinjected into the formation to move the material slug through theformation. lntermittently, additional slugs of material are injectedinto the well.

Other modifications and alterations of this invention will becomeapparent to those skilled in the art from the foregoing discussion, andit should be understood that this invention is not to be unduly limitedthereto.

What is claimed is:

1. A method for recovering hydrocarbons from a subterraneanhydrocarbon-containing formation penetrated by at least one injectionwell and at least one remotely located producing well, comprising:

injecting a substantially continuous stream of floodwater downwardlythrough the injection well and into the formation; intermittentlyinjecting a volume of viscous viscosity-increasing material into thefloodwater and the formation at a plurality of spaced-apart timeintervals;

intermittently injecting a volume of gel particles into the floodwaterand the formation at a plurality of spacedapart time intervals, said gelparticles being a material different from said viscosity-increasingmaterial, being selected from the group consisting of partiallyhydrolyzed polyacrylamides gelled with polyvalent metal ions orformaldehyde and lignosulfonate gelled with sodium dichromate, and beinginjected at intervals separated from said viscosity-increasing material;and

producing to the surface the hydrocarbons entering the producing well.

2. A method, as set forth in claim 1, wherein the viscosityincreasingmaterial is selected from a group consisting of par tially hydrolyzedpolyacrylamides, carboxymethyl cellulose,

or guar gum.

3. A method, as set forth in claim 1, wherein the portion of thetloodwater having gel material therein has a gel material concentrationin the range of about 0.1 percent to 0.001 percent by volume.

4. A method, as set forth in claim 1, wherein the portion of thefloodwater having viscosity increasing material therein has aviscosity-increasing material concentration in the range of about 0.05percent to 0.1 percent by volume.

5. A method, as set forth in claim 1, further including a volume ofsurfactant mixed with the viscosity-increasing material, and saidviscosity-increasing material concentration being in the range of about0.05 percent to 0.020 percent by volume.

6. A method, as set forth in claim 1, wherein each portion of floodwatercontaining viscosity-increasing material is injected into the formationand immediately followed by a portion of floodwater containing gelparticles.

7. A method, as set forth in claim 1, wherein the volume of gelparticles injected into the formation is greater than the volume ofviscosity-increasing material injected.

8. A method, as set forth in claim 1, wherein the floodwater,viscosity-increasing material, and gel particles are injected into theformation through a plurality of spaced-apart injection-wells.

9. A method as set forth in claim 1, wherein injected volumes offloodwater and viscosity-increasing material and floodwater and gelparticles are followed by a volume of only floodwater.

2. A method, as set forth in claim 1, wherein the viscosity-increasingmaterial is selected from a group consisting of partially hydrolyzedpolyacrylamides, carboxymethyl cellulose, or guar gum.
 3. A method, asset forth in claim 1, wherein the portion of the floodwater having gelmaterial therein has a gel material concentration in the range of about0.1 percent to 0.001 percent by volume.
 4. A method, as set forth inclaim 1, wherein the portion of the floodwater having viscosityincreasing material therein has a viscosity-increasing materialconcentration in the range of about 0.05 percent to 0.1 percent byvolume.
 5. A method, as set forth in claim 1, further including a volumeof surfactant mixed with the viscosity-increasing material, and saidviscosity-increasing material concentration being in the range of about0.05 percent to 0.020 percent by volume.
 6. A method, as set forth inclaim 1, wherein each portion of floodwater containingviscosity-increasing material is injected into the formation andimmediately followed by a portion of floodwater containing gelparticles.
 7. A method, as set forth in claim 1, wherein the volume ofgel particles injected into the formation is greater than the volume ofviscosity-increasing material injected.
 8. A method, as set forth inclaim 1, wherein the floodwater, viscosity-increasing material, and gelparticles are injected into the formation through a plurality ofspaced-apart injection-wells.
 9. A method as set forth in claim 1,wherein injected volumes of floodwater and viscosity-increasing materialand floodwater and gel particles are followed by a volume of onlyfloodwater.